A storage appliance can manage storage and replication of data to multiple tiers of storage. Tiers of storage can include an active tier, a cloud tier, a remote tier, an archive tier, and other tiers of storage. The multiple tiers of storage, collectively termed a storage system, can have a single namespace for accessing files on the multiple tiers. The namespace may be stored in a tree structure, such as a b-tree. A storage appliance can store and manage a large plurality of namespaces, each stored as, e.g., a b-tree, and linked together in a single data structure for the large plurality of namespaces. To expose a namespace of a multi-tier storage system to one or more users, the namespace of the storage system may stored on an active tier of storage, such as a storage appliance. A storage appliance may perform various storage system operations that are directed to one tier of the storage system, utilizing the namespace that references the multiple tiers of the storage system. Storage system operations may include replication of files or data from one tier to another, renaming or deleting of files, and other file system operations. As a prerequisite to a storage appliance operation, a snapshot of the namespace and data space of the storage may be needed.
One of the problems with performing tier-specific snapshots in a multi-tier storage environment using a single namespace that references the multiple tiers, is that the storage space in multiple tiers of the storage system is locked out. Customers may want to have the ability to take a snapshot only in a particular tier. In the prior art, taking a snapshot of a particular tier in a mutli-tier storage system can lock files across multiple tiers to perform a multi-tier file system operation, in part because the namespace of the multi-tier storage system spans the multiple tiers.